Gasoline



Patented Feb. 19, 1946 GASOLINE Ernest L. Walters, San Francisco, Calif., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application May 1, 1943, Serial No. 485,553

7 Claims.

This invention relates to high octane gasolines having improved oxidation stability. More particularly it pertains to a method for the improvement of the storage stability of leaded saturated gasoline type motor fuels and to combinations of ingredients particularly efiective in small quantitles in restraining the oxidative decomposition of such leaded fuels.

A principal purpose is to provide gasoline type motor fuel of greater stability and ,decreased age deterioration. Another object is to produce aviation gasolines which are both high in octane rating and low in gum forming or precipitating tendencies. A further purpose is to provide new and improved inhibitors for leaded saturated gasoline type motor fuels. Other objectives will be apparent from the following description.

In my copending application Serial No. 441,876, filed May 5, 1942, I showed that 2,4-dimethyl-6- tertiary butyl phenol possesses unique and extraordinary inhibitor powers for tetra-alkyl lead fluid as well as for an initially stable gasoline (such as substantially saturate gasolines, for example aviation gasoline, as distinguished from unstable or cracked gasoline), which stable gasoline has been rendered unstable by the addition of tetraalkyl lead.

I have now found that the addition of small quantities of both 2,4-dimethyl-6-tertiary butyl phenol and an alkyl phenylene diamine in which each alkyl radical contains from three to six carbon atoms still further increases the stability of an initially stable gasoline containing tetraalkyl lead. Gasolines which are susceptible to this treatment for retarding their decomposition are relatively stable compositions such as straight run or casing head gasoline, alkylate fractions such as iso-octane, and the like. Although such hydrocarbons have a comparatively long life when stored alone, their age decomposition is tremendously accelerated when the conventional quantity (up to about 6 cc./gal.) of tetra-alkyl lead is added to the fuel to increase its knock rating. In such a gasoline, it is primarily the tetra-alkyl lead which disintegrates at a fairly rapid rate upon standing, so that the natural life of the gasoline is greatly shortened by the occurrence of a precipitate of high lead content.

My alkyl phenylene diamines have the formula in which R represents a hydrogen atom or an alkyl group having from three to six carbon atomsthat is n-propyl, isopropyl, n-, lso-, secondary and tertiary butyl, primary, secondary and tertiary amyl and the various hexyl radicals. The several Rs may be the same or difierent radicals and at least one R in each molecule must be one of the designated alkyl radicals. The di-, triand tetra-alkyl compounds are preferred due to their greater solubility in the motor fuel. Normal and secondary butyl have been found especially efiective alkyl radicals in these compounds, particularly so when they occupy all four of the R'positions in the formula. The para form of the phenylene diamine is preferred although the ortho and meta compounds may be used, and

15 the nucleus may also be substituted with alkyl radicals.

My invention may be illustrated by the following oxidation induction measurements carried out at 110 C. and 100 p. s. i. oxygen pressure. The

gasoline used was a 100 octane aviation gasoline treated to remove all natural inhibitors. It was composed of 45% straight run gasoline, 45% alkylate material and 10% isopentane plus 4 cc./gal. terta-ethyl lead. In the absence of tetra-ethyl lead, the induction period of this gasoline was over hours.

1 2,4-dimethyl-6'tertiary butyl phenol. The calculated induction period was obtained by adding the observed individual induction periods of the two inhibitors and subtracting th induction period of the leaded gasoline without any inhibitor. It will be seen that not only was the observed induction period for 0.25 mg./100 ml. of 2,4-dimethyl-6-tertiary butyl phenol plus 0.25 mg./l00 ml. N N dibutyl p phenylene diamine greater than the calculated induction period but it was also reater than the observed induction period of 0.5 mg. of 2,4-dimethy1-6-tertiary butyl phenol.

I have also found that just as 2,4-dimethyl-6- 55 tertiary butyl phenol is unique as an. inhibitor for tetra-alkyl lead among the many inhibitors known for cracked gasoline, so the association of 2,4-dimethyl-6-tertiary butyl phenol with these alkyl phenylene diamines is a unique combination of enhanced inhibitors for initially stable fuels containing tetra-alkyl lead. Analogous combinations of amines and phenols do not produce this enhanced induction period with leaded saturate gasoline. Indeed many combinations of known amine and phenol gasoline inhibitors were found to produce induction periods for the leaded aviation gasoline which were not only much less than the calculated induction period but also less than the induction period of but one of the inhibitors alone. This was found to be the case for "0.5 mg./100cc. concentrations of 2,4-dimethyl-- fi-tertiary butyl phenol in association respectively with 0.5 mg. concentrations of a naphthol and alkyl phenolsboiling between 220 and 240 C. A similar depression was also observed in combinations of m naphthol with alkyl phenols boiling between 220 and 240 C. and with N N dibutyl p phenylene diamine respectively.

Although 2,4dimethyl-6-tertiary butyl phenol and the described alkyl phenylene diamine inhibitors may effectively be associated in a gasoline in any ratio, I prefer to employ a minimum of 25% of either inhibitor in relation to the total amount of both inhibitors. In general, suitable amounts of this pair of inhibitors in a gasoline is between about 0.0001% and 0.01% and more preferably between about 0.0005% and 0.005%.

1. A stable motor gasoline consisting essentially of a normally stable gasoline type motor fuel containing an amount of tetra-alkyl lead suflicient to render the mixture relatively unstable on storage, and a stabilizing amount of a mixture of 2,4-dimethyl-6-tertiary butyl phenol and a phenylene diamine having at least one, three-to-sixcarbon atom alkyl radical attached to a nitrogen atom.

2. The composition of claim 1 in which the phenylene diamine is a para phenylene diamine.

3. The composition of claim 1 in which the phenylene diamine is N N di nalkyl para phenylene diamine.

4. The composition of claim 1 in which the phenylene diamine is N N' dibutyl para phenylene diamine.

5. The composition of claim 1 in which the phenylene diamine is N N' di secondary butyl para phenylene diamine.

6. An initially stable aviation gasoline containing about 0.0001% to 0.01% of 2,4-dimethyl-6- tertiary butyl phenol, about 0.0001% to 0.01% N N dibutyl para phenylene diamine and up to about 6 cc. per gallon of tetra-ethyl lead.

7. In combination, a major portion of an in-' itially stable gasoline and dissolved in said gasoline a minor portion of tetra-alkyl lead fluid containing a stabilizing amount of a mixture of 2,4-

dimethyl-S-tertiary butyl phenol and an N N dialkyl para phenylene diamine in which the alkyl groups attached to the nitrogen atoms contain between three and six carbon atoms.

ERNEST L. WALTERS. 

